Warren banks $8.6 million in second-quarter fundraising

The campaign touted Warren's grassroots support, noting that 81 percent of donations to the campaign were of $50 or less and more than half were $25 or less.

Incumbent Sen. Scott Brown (R-Mass.) has not yet released his fundraising numbers for the second quarter. Warren outpaced Brown in the first quarter, more than doubling his $3.4 million by bringing in $6.9 million — more than any other congressional candidate during that period. But Brown benefited from a running start, reporting $15 million in the bank on March 30, compared to about $11 million for Warren, thanks to $7 million rolled over from his 2010 special election.

Brown's campaign looked to dismiss the numbers as driven by out-of-state donors in a statement Monday.

"Professor Warren’s campaign is largely dependent on out-of-state, extreme special interests and fellow Occupy protestors who share her radical tax, borrow and spend agenda," said Brown spokeswoman Allegh Marre. "Ultimately, however, elections are decided by the voters based on competing visions for our future, and Scott Brown will have the resources he needs to share his pro-jobs message and independent record with voters across the Commonwealth. No amount of money can wash away Professor Warren’s support of job-crushing tax hikes that would devastate our economy, especially in the wake of Friday’s incredibly weak employment report."

The ability of candidates to fundraise for their campaign is especially important in the Massachusetts race, where Warren and Brown have entered into an agreement that forces them to donate a matching amount to charity every time an outside group spends on their behalf.